Evolution of conditional cooperation in a spatial public goods game

Spatial structure is one of the mechanisms that allows the evolution of cooperation, especially in dyadic interactions. However, when interactions occur within groups, the effectiveness of spatial structure is reduced, and additional mechanisms to sustain cooperation are needed. Conditional cooperation strategies are commonly adopted in strategic interaction, but not extensively investigated in the context of spatial reciprocity, despite potentially changing the dynamic of the evolution of cooperation. We propose and model a public good game where agents spatially interact in groups and adopt conditional cooperation strategies. We show that cooperation is evolving with no need for additional mechanisms apart from spatial structure when agents follow conditional strategies. We confirm the positive influence of productivity and cluster formation on the evolution of cooperation in spatial models. Our results are robust for two types of conditional cooperation strategies.